1. Field of the Invention
The present invention relates to an air gap adjusting apparatus for a cylindrical linear motor of an elevator.
2. Description of the Conventional Art
Conventionally, the cylindrical linear motor includes a cylindrical rotor having a longitudinal bore of a predetermined diameter therethrough and a longitudinal stator slidably engaged within the longitudinal bore hole of the rotor. The rotor moves along the stator by means of a magnetic force generated between the inner surface of the rotor and the outer surface of the stator with a predetermined gap therebetween.
Referring to FIG. 1, there is shown a cylindrical linear motor-driven elevator including a rectilinear hexahedron frame formed of a plurality of reinforced steel bars connected together at the ends thereof. A stator 38 made of electrically conducting materials is disposed in parallel between the rear-most two vertical bars A and B with one end of the stator 38 being attached to a central position of the upper rear bar C and the other end of the stator 38 being connected to a fixing unit 42 connected to a central position of the lower rear bar D.
A front supporting shaft 10 carrying a plurality of pulleys 12 rotatably engaged thereon is provided, with its one end being connected to a front end of the upper left bar E and its other end being connected to a front end(not shown) of the upper right bar F. A rear supporting shaft 10a having a plurality of pulleys 12a rotatably carried thereon is provided, with its one end being connected to a rear end of the upper left bar F and its other end connected to a rear end of the upper right bar E. Mounted to each front vertical bars G and H is provided a front guide rail 20 extending therealong from their upper end to lower end. Also, there is mounted a rear guide rail 32 on each of the rear two bars A and B. A substantially rectilinear hexahedral box-shaped cage 16 is suspended by a plurality of metal cables 14, via four pulleys 12 and 12a, with its one of the ends being connected to an upper surface of the cage 16 and with the other ends being connected to the upper portion of a rectilinear hexahedron frame 24. On the left and fight outer surfaces of the cage 16 am provided a plurality of rollers 22 which enable a slidable movement of the cage along the front guide rails 20. The frame 24 whose upper bar is connected with an end of the ropes 14 slidably moves along the rear guide rails 32. The frame 24 has a hole formed through the central positions of both an upper bar and lower bar thereof, for enabling the stator 38 to pass through the frame 24 and the rotor 28 which is vertically affixed at a central position of the frame 24, thereby permitting the rotor 28 to move slidably along the stator 38. The rotor 28 receives the stator 38 via the bore hole thereof. At a bottom end of the rotor 28, a control unit 30 is mounted just under the frame 24. And, a plurality of counter weights 26 made of heavy-weight materials are provided in the left and right inside portions of the frame 24 for facilitating the cylindrical linear motor to operate with less drive force when the cage 16 moves upwardly.
Referring to FIG. 2, there is shown a conventional air gap adjusting apparatus for a cylindrical linear motor of an elevator. FIG. 3 shows a cross-sectional view taken along line III--III of FIG. 2. The conventional air gap adjusting apparatus includes a plurality of adjusting units 50 mounted at an outside upper portion of the rotor 28. The rotor has a longitudinal bore hole extending centrally therethrough. Stator 38 is slidably inserted within the bore hole of the rotor 28. Each adjusting unit 50 includes a roller 46 having a rotatable supporting pin 48 fixedly affixed to each side of the roller 46. A spring 52 is connected between the end of each supporting pin 48 and a rear inner surface of the adjusting unit 50. In both side surfaces of the adjusting unit 50 is provided an elongated slot 50a having a predetermined diameter and length for receiving the supporting pins 48 therein.
The operation of the conventional air gap adjusting apparatus for a cylindrical linear motor of an elevators is described below.
When electric power is supplied to the rotor 28 and the stator 38, an electromagnetic force is generated with its force and direction depending upon the supplied electric power. As a result of this electromagnetic force the rotor 28 moves linearly along the stator 38. At this time, there is always maintained an air gap between the inner surface of the rotor 28 and the outer surface of the stator 38 for enabling the rotor 28 to move smoothly therealong. During operation of the elevator there may occur some vibrations or an unbalanced load in the cage because passengers in the cage are positioned randomly. Therefore, these vibrations and unbalanced loads are transferred to the rotor 28 via the metal cables 14, shown in FIG. 1, so that there can occur some vibration between the inner surface of the rotor 28 and the outer surface of the stator 38 and the unbalanced loading therebetween. To compensate for vibrations and unbalanced load therebetween, the adjusting units 50 are provided. When the adjusting unit 50 receives those vibrations and unbalanced load, the roller 46 which is made as an elastic member absorbs the impact with its elastic properties and moves backwardly along the elongated slot 48. The spring 48 further counteracts the impacts therefrom. Therefore, the air gap between the inner surface of the rotor 28 and the outer surface of the stator 38 is always maintained at a predetermined distance therebetween.
However, when only one or more roller become worn out due to the unbalanced load in the cage there have been no measures available to adjust each of the rollers because the size of the rollers and the springs are previously determined by the manufacturer, so that it cannot be adjusted correctly, respectively.
Referring to FIG. 4, there is shown an air gap variation detecting apparatus for detecting a malfunction in the air gap maintained between the outer surface of the rotor 28 and the inner surface of the stator 38. It includes a cuff-shaped casing 58 surrounding the stator while not being in contact with an outer surface of the stator 38, a fixing screw 59 provided at a lower portion of the casing 58, a contact sensor 57 whose one end is electrically connected to one end of the fixing screw 59 and whose other end is positioned by means of a tightening screw 55 so that it is not electrically in contact with the outer surface of the stator 38 when a proper air gap is maintained. The other end of the fixing screw 59 is connected with a terminal 53 of DC(Direct Current) 52. A DC terminal 52 is also connected to internally the stator 38.
The operation of the conventional air gap variation detecting apparatus is as follows. When there is a malfunction in maintaining a gap distance between the outer surface of the rotor 28 and the inner surface of the stator 38, the contact sensor 57 comes into electrical contact with the outer surface of the stator 38, so that there a warning lamp(not shown) is lighted, and thus the elevator stops. In addition, there can be a slight volume expansion between the outer surface of the rotor 28 and the inner surface of the stator 38 due to heat generated by the continuous operation of the elevator. As a result of the expansion between the inner surface of the rotor 28 and an outer surface of the stator 38 there may often occur contact between the contact sensor 57 and the outer surface of the stator 38 thus causing frequent malfunctioning of the elevator.